Method for routing ip-packets to an external control comonent of a network node in an ip-packet switching communications network comprising several network nodes

ABSTRACT

According to one embodiment, IP-packets are received, identified, evaluated and processed at interfaces of a network node. An IP-tunnel is established from each interface of the network node to the control component. An in-band IP signaling packet, which is received at an interface of the network node and characterized by an entry in the protocol field of the header of the IP-packet, is routed through the IP-tunnel to the control component.

CROSS REFERENCE To RELATED APPLICATIONS

This application is the US National Stage of International ApplicationNo. PCT/EP2004/050950, filed May 27, 2004 and claims the benefitthereof. The International Application claims the benefits of Germanapplication No. 10324604.5 DE filed May 30, 2003, both of theapplications are incorporated by reference herein in their entirety.

FIELD OF INVENTION

The invention relates to a method for routing IP packets to an externalcontrol component of a network node in an IP packets switchingcommunications network.

BACKGROUND OF INVENTION

Internet protocol networks (IP networks for short) will in futuretransport higher-quality services in addition to the current standardInternet and best-effort services, and will permit new applications. Tothis end enhancements to the control of the network nodes of an IPnetwork or of the network controller are necessary, e.g. foradministering the network resources or for fast reconfiguration in theevent of errors.

In general the alternatives are to:

-   integrate control components into the network components, network    nodes and/or network elements such as routers, or-   link control components as external servers to the network    components, network nodes or routers to be controlled. This can be    done directly, i.e. by a connection or line between an external    interface of the network component and the control component    situated in the vicinity, or via a network connection between    network component and control component.

The first integrated solution has the advantage that internalinformation in the network component is available to the controlcomponent thanks to the close link to the network component.

In contrast to this an “add-on” solution is vendor-independent and moreflexible, precisely because it is not so closely interwoven with theinternal aspects of the network component. In addition, “add-on”solutions can be based on standard hardware (HW for short) and software(SW for short) solutions, while network components such as routers aremostly based on proprietary HS/SW solutions. Shorter development cyclesand cost savings can be achieved with “add-on” control components. Thedrawback of “add-on” solutions is that internal information in thenetwork component is not available.

Using the example of an admission control (AC for short) component theproblem of the second, external, “add-on” server solution is illustratedbelow.

One object of admission control is to accept incoming resource queries,compare them with resources still available and if resources are stillavailable to program a network node or router, e.g. the router on theedge of the network (edge router) for control of the data flow. Thisincludes setting what are known as functions, such as marking, filteringand policing.

The following two questions arise here, among others:

-   A) How do the resource queries reach the add-on control component or    admission control?-   B) How can the control component or admission control and configure    the network node and from where does the control component obtain    the necessary information about the internal aspects of the network    component, e.g. at what interface was a packet received and what    interface needs to be configured?

In principle, there are two variant solutions for A):

-   1) The data path which the IP packets take is known and accordingly    the control component or admission control can be addressed    directly. This is called “out-band signaling”.-   2) The signaling protocol follows the path of the data packets and    thus finds the control component or admission control automatically.    This is called “in-band signaling”.

The following is based exclusively on signaling in accordance withvariant 2), in other words in-band signaling.

The standardized resource reservation protocol RSVP is an in-bandsignaling protocol. It solves the questions outlined above as describedunder point 2) and performs a hop-by-hop reservation in the networknode. The key point here is that the RSVP instance is implemented in therouter itself and hence can operate with the router and its internalaspects on a very close-meshed basis.

Using the example of an RSVP-capable network, i.e. of a network withRSVP-capable network nodes or routers in accordance with FIG. 1, theprocedure will be described schematically.

FIG. 1 shows a schematic IP network, consisting of a plurality ofnetwork nodes or routers A to H, which in each case have a controlcomponent AC internally. The network node A is on the one hand connectedby a series connection of the network nodes B, C, D and on the otherhand by a series connection of the network nodes F, G, H to the networknode E. The network nodes B and G, C and H as well as D and H arelikewise connected to one another. The connections or connection pathsare for example implemented as electrical or optical lines, such astwo-wire lines, coaxial cable or optical fiber conductors. A user X isconnected at network node A and a user Y is connected at network node E.

The user X generates a resource request to the network for a data flowto user Y. It must be ensured here that the resource reservations in thenetwork nodes are also in fact undertaken along the subsequent datapath. In IP networks this data path depends on the current routing.Hence in the resource reservation protocol RSVP the resource request issent into the network with the IP destination address, in other wordsthe IP address of the user Y. It thus automatically follows the datapath of the subsequent data flow to user Y. Although these RSVP messagesare now not addressed to the RSVP control components AC or RSVPinstances, the RSVP control components AC or RSVP instances of thenetwork nodes lying on the path must be notified of them.

Hence these messages are specially marked by the defined IP protocoltype “RSVP” in the IP header, in other words in the header of an IPpacket.

The routers identify this protocol type and route messages marked inthis way directly to their RSVP instance, in other words to the controlcomponent AC.

Later, in the course of the procedure, the RSVP instance must configure“its” edge router A on the edge of the network to user X (filtering,marking, policing). In concrete terms, the interface to be configured isthe one via which the RSVP message was originally received from user Xand via which the data flow from user X to user Y will subsequentlyarrive. Since the RSVP instance is implemented in the router, it caninterrogate this internal information.

The solution for the two points A and B lies here in the close internallink between network node and control component.

-   Re A) The resource queries reach the control component via special    filters in the network node or router, which identify the protocol    ID and forward the packets directly past the routing to the internal    control component.-   Re B) The control component AC receives information on the    configuration of the network node or router by accessing    router-internal data.

In the case of external control components the problem exists that thisinternal information is not interrogated in the case of the network nodeor made available by the network node. A further problem exists if theexternal control components of the network node are not provided theretodirectly, but are located at a very remote place in the network and canonly be reached via a network connection.

SUMMARY OF INVENTION

An object of the present invention is to specify a method in whichreceived IP packets can be routed with interface information in thereceiving node to an external control component.

This object is achieved by methods in accordance with the features inthe claims.

The advantage of the invention is that IP packets are routed withnetwork-node-internal control information to an external controlcomponent. As a result a control component “added on” to a network nodecan assume comprehensive control tasks of the network node.

Another advantage is that the external control component can be disposedat a remote location in the network and is connected via a networkconnection.

Advantageous developments of the invention are specified in the d.

Brief Description Of The Drawings An embodiment of the invention isillustrated in the drawing and is explained in the following.

The drawings show:

FIG. 1 A schematic IP network with network-node-internal controlcomponents AC in accordance with the prior art.

FIG. 2 An IP network structured analogously to FIG. 1 with two externalcontrol components AC in accordance with the invention.

DETAILED DESCRIPTION OF INVENTION

FIG. 1 shows an IP network in accordance with the prior art alreadyexplained in the introduction to the description.

FIG. 2 shows a network in accordance with FIG. 1, with the differencethat in each case an external control component AC is connected at thenetwork elements D and G.

Analogously to the example referred to in the introduction to thedescription, data packets are to be transferred from user X to user Y.The external control components AC here require particular IP packets,such as in-band IP signaling packets, for example RSVP packets, and theinformation about which interface of the network node the IPpacket/in-band IP signaling packet/RSVP packet was received at. Thelatter information is only available internally in the network node andcannot be interrogated. The routing tables of the network node or routercontain only information about destinations, but not about where apacket came from.

To solve the problem, rules are configured on the interfaces of thenetwork nodes. Current network nodes or routers support what is known aspolicy routing, whereby rules can be configured for how to deal withspecial packets. Moreover, use is made of what is known as tunneling.

Using IP tunnels, e.g. GRE tunnels, the original IP packet issupplemented at the tunnel entrance by a tunnel header including atunnel ID and a new external IP header. The IP packet is routed throughthe network with this IP header. At the end of the tunnel the externalheader is removed again and the original packet is further processed.

Modern network nodes or routers, in particular the edge routers involvedhere, often support one or more variants of tunneling.

The solution using tunnels is based on the fact that several tunnels canbe set up from the network node or router (start of the tunnel) to thecontrol component AC or control instance (end point) and can bedistinguished by their tunnel identification number (tunnel ID forshort) in the tunnel header.

A first variant consists in using the tunnel ID to transfer internalinformation. Thus for each interface of the network node a separatetunnel is set up to the control component, so that the interface numbercorresponds explicitly or implicitly to the tunnel ID.

To this end a tunnel is set up from each interface of the network nodeto the control component. To do this, a rule is set up in the networknode or on the interface, that particular IP packets, such as in-band IPsignaling packets which are marked by an entry in the protocol field ofthe IP header of the IP packet, are packed in a second, “external” IPpacket, the IP address of the control component assigned to the networknode is entered as the destination IP address in the “external” IPpacket and a value unambiguously assigned to the interface which differsfrom the values of the other interfaces of the network node and withwhich the interface can be unambiguously identified, is entered as atunnel ID in the “external” IP packet. This packet is forwarded by theIP routing to the control component. In similar fashion, in-band IPsignaling packets of the type “RSVP” are packed and transmitted.

The advantage of this tunnel solution is that the control components orcontrol instances need not be connected directly to the network node orrouter, but can be positioned anywhere in the network, as illustrated inFIG. 2 by way of example by the control components AC at the networknodes D and G. The control components AC can then be reached via thelogical “direct interface” tunnel.

In a parallel patent application by the applicant a solution for asimilar object is proposed using what is known as DSCP marking. In thecase of a particular received IP packet, such as an in-band IP signalingpacket of the type “RSVP”, the value of a particular field, such as theDSCP field, the IP header or header field of the IP packet, is herechanged and a value dependent on the receiving interface of the networknode is entered into the particular header field/DSCP field. Thissolution can be combined with the tunnel solution. Thus tunnels can beset up and in addition the DSCP fields of an IP packet can be modified.

The rules on the interfaces of the network nodes then contain acorresponding marking, such as DSCP marking, and the correspondingtunnel as the “next-hop” entry.

In the following the DSCP field is assumed to be the field to bechanged, but another field in the header of the IP packet can also beused.

If DSCP marking and tunneling is used, a DSCP field change or a DSCPmarking should be undertaken on the internal IP header. The external IPheader can then actually be used for DSCP priority marking.

Moreover the tunnel ID need no longer contain a value assigned to theinterface, since this value is unambiguously entered into the DSCPfield.

In addition there is no need for a tunnel to the assigned controlcomponent to be set up from every interface. Thus at least one tunnel tothe control component could be set up from the network node, whereby allIP packets of a particular type, such as in-band IP signaling packets,e.g. “RSVP” packets, are transmitted to the control component and thedistinction as to which interface the packet was received at is made bythe changed DSCP field.

Since the DSCP field is 6 bits in size, permitting a range of 64 values,the available value range is increased by a combination of tunneling andDSCP marking. As a result a large range can be covered with few tunnels.Using e.g. 2 tunnels and DSCP marking it is thus possible to distinguish128 values or interfaces of the network node.

Tunneling can also be achieved by multiprotocol label switching, MPLSfor short. The method is analogous to IP tunnels, with the differencethat MPLS “tunnels” or MPLS paths are used instead of the IP tunnels.

With multiprotocol label switching, MPLS for short, states aremaintained network-wide which define the routes or paths on whichpackets are routed through the network circumventing the “normal” IProuting. The network nodes here no longer route packets on the basis ofthe destination IP addresses, but a bit sequence, known as a label, isattached to each packet on entrance to the network. This label, which isevaluated in every network node, determines the route on which thepackets are forwarded. The correlation between labels and paths must becreated when the network is commissioned. The label is removed again atthe network exit. In addition local mechanisms or rules are required todivert packets onto a backup path if the path originally envisagedcrashes, or to establish a backup path after a crash.

An in-band IP signaling packet or an IP packet of the type “RSVP”, or ofanother type, received at an interface of the network node is identifiedhere and an MPLS label is prefixed to the packet, the label ID of whichis unambiguously assigned to the receiving interface and leads to thecontrol component assigned to the network node. The IP packet packed inthis way is routed to the control component by means of MPLS. The MPLSlabel ID prefixed to the IP packet is evaluated in the control componentand the interface on which the IP packet was received from the networknode is determined in the control component.

On the interface of the network node the rule is implemented that aparticular value, permanently defined for the interface, is prefixed tothe IP packet as an MPLS label and the packet is routed using MPLS.Using the MPLS method it must be ensured that packets with a particularMPLS label ID lead to the corresponding destinations, in this example tothe control component.

In this case too MPLS can be combined with DSCP marking, in similarfashion to the method described above. Here it is sufficient if at leastone MPLS label ID is entered in the network node, since the interfacesof the network node are distinguished by the DSCP marking.

For example, an in-band IP signaling packet or a packet of the type“RSVP” received at an interface of the network node is identified and isprocessed such that the value of a particular field, such as of the“DSCP” field, is changed as a function of the receiving interface. Forexample, an unambiguous interface ID, which differs from the interfaceID of the other interfaces of the network node, is entered into the DSCPfield, an MPLS label is further prefixed to the IP packet and thischanged packet is routed by the MPLS method to the control component. Itis not necessary here for every interface to enter a separate MPLS labelID, since the interfaces are distinguished by the DSCP field. Likewiselarge value ranges can be achieved by combining MPLS label ID and DSCPmarking. Using e.g. 2 MPLS label IDs and DSCP marking it is possible todistinguish 128 values or interfaces of a network node.

1-9. (canceled)
 10. A method for routing Internet Protocol (IP) packetsto a control component external from a network node in an IP packetswitching communications network, comprising: providing a network nodehaving a plurality of interfaces; setting up an IP tunnel to an externalcontrol component from each interface of the network node; receiving anin-band IP signaling packet at one of the plurality of interfaces, thepacket marked by an entry in a protocol field of a header in the packet;and routing the packet through the IP tunnel to the external controlcomponent.
 11. The method according to claim 10, wherein the receivedpacket is an “RSVP” type packet.
 12. The method according to claim 12,wherein the external control component is directly connected to thenetwork node.
 13. A method for routing Internet Protocol (IP) packets toa control component external from a network node in an IP packetswitching communications network, comprising: providing a network nodehaving a plurality of interfaces; assigning a unique value to eachinterface; setting up at least one IP tunnel to an external controlcomponent from the network node; receiving an in-band IP signalingpacket at one of the plurality of interfaces, the packet marked by anentry in a protocol field of a header in the packet; changing a field inthe header of the packet to include the value associated with thereceiving interface; and routing the changed packet through the IPtunnel to the external control component.
 14. The method according toclaim 13, wherein prior to routing the changed packet, the methodfurther comprising, identifying the received packet as an “RSVP” typepacket, and changing a “DSCP” field in the header as a function of thereceiving interface.
 15. The method according to claim 14, wherein therouting is based on an MPLS method and prior to routing the changedpacket, the method further comprising, identifying the received packetas an “RSVP” type packet, and prefixing to the packet an MPLS labeldependent on the receiving interface.
 16. The method according to claim16, wherein the external control component is directly connected to thenetwork node.
 17. A method for routing Internet Protocol (IP) packets toa control component external from a network node in an IP packetswitching, MPLS-capable communications network, comprising: providing anetwork node having a plurality of interfaces; receiving an in-band IPsignaling packet at one of the plurality of interfaces, the packetmarked by an entry in a protocol field of a header in the packet;prefixing a MPLS label to the packet; and routing the changed packetthrough to the external control component via an MPLS method.
 18. Themethod according to claim 17, wherein prior to routing the changedpacket entering into a field in the header of the packet a valueassociated with the receiving interface, the value different thananother value on the non-receiving interface.
 19. The method accordingto claim 18, prior to routing the changed packet, the method furthercomprising, identifying the received packet as an “RSVP” type packet,and changing a “DSCP” field in the header as a function of the receivinginterface.